| With the implementation of the "one belt and one way" strategy in China,North China as an important window for opening up to Northeast Asia,the demand for traffic construction is growing.Most of these areas are loess covered areas,and tunnel construction will inevitably encounter such special soil.Compared with the general soil,loess has more complex soil-water characteristics and engineering characteristics.The stability of tunnel engineering with loess as its main body has always been the focus of research in the engineering field.Previous studies have rarely shown the unsaturated characteristics of Loess tunnels,and the results are conservative.Based on a part of the Loess Section of Pingshan-Zanhuang Expressway Project,the shear strength of unsaturated loess under different confining pressures and suction of different matrices and the whole process curve of soil-water characteristics of undisturbed loess samples were measured by indoor unsaturated triaxial test and Soilwater characteristic curve test.The data obtained from soil-water characteristic curve test were fitted by using Matlab software.With the selection of mathematical model,according to the fitting results,the best fitting effect between mathematical model and test data points is obtained under Fredlund & Xing3 parameters.Then,on the basis of the previous experimental part and the available data,the stability of tunnel surrounding rock under different working conditions is analyzed by Midas software,and the stress displacement and plastic zone values under different rainfall duration,rainfall intensity,saturation and permeability coefficient are simulated,and the rainfall duration and rainfall intensity are analyzed.The influence of degree,saturation and permeability coefficient on the stability of surrounding rock of tunnel provides theoretical basis for construction,operation and maintenance of Loess tunnel. |
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